composer: yum.YumBase can be called only once per programm it leaves open files

if called multiple times yum.YumBase leaves open files even if you call
close() on it it still leaves the /var/log/yum.log log file open
blotter: use consistently PluginManager.getSwirl to create new swirl file

sometimes it was using self.swirl.createSwirlFile and sometimes
PluginManager.getSwirl, now it always uses PluginManger
swirl: normalize path before storing them inside the swirl
composer: log more stuff when creating the roll

switched also some print to logger
composer: make_roll process openedFiles even when we find an RPM

given a swf even if we find an RPM to supply it's capabilities
process its openedfiles
composer: make_roll: include all file from a package only if swf is not an ELF

if we select the libmpi.so.2 we also want to carry all its dynamic libraries
even if their name matches an available package for this reason we use wanted_pcks

but we should trigger this wated_pcks mechanism only if the swf is an ELF